\ | Marks the next character as either a special character or a literal. For example: - n matches the character n. "\n" matches a newline character.
- The sequence
\\ matches \ and \( matches ( . |
^ | Matches the beginning of input. |
$ | Matches the end of input. |
* | Matches the preceding character zero or more times. For example, "zo*" matches either z or zoo. |
+ | Matches the preceding character one or more times. For example, "zo+" matches zoo but not z. |
? | Matches the preceding character zero or one time. For example, a?ve? matches the ve in never . |
. | Matches any single character except a newline character. |
( subexpression) | Matches subexpression and remembers the match. If a part of a regular expression is enclosed in parentheses, that part of the regular expression is grouped together. Thus a regex operator can be applied to the entire group. - If you need to use the matched substring within the same regular expression, you can retrieve it using the backreference (
\num , where num = 1..n ). - If you need to refer the matched substring somewhere outside the current regular expression (for example, in another regular expression as a replacement string), you can retrieve it using the dollar sign (
$num , where num = 1..n ). - If you need to include the parentheses characters into a subexpression, use
\( or \) . |
x | y | Matches either x or y. For example, z|wood matches z or wood. (z|w)oo matches zoo or wood. |
{n } | n is a nonnegative integer. Matches exactly n times. For example, o{2} does not match the o in Bob, but matches the first two o's in foooood. |
{n ,} | n is a nonnegative integer. Matches at least n times. For example, o{2,} does not match the o in Bob and matches all the o's in "foooood." o{1,} is equivalent to o+ . o{0,} is equivalent to o* . |
{ n , m } | m and n are nonnegative integers. Matches at least n and at most m times. For example, o{1,3} matches the first three o's in "fooooood." o{0,1} is equivalent to o? . |
[ xyz] | A character set. Matches any one of the enclosed characters. For example, [abc] matches the a in plain. |
[^ xyz ] | A negative character set. Matches any character not enclosed. For example, [^abc] matches the p in plain. |
[ a-z ] | A range of characters. Matches any character in the specified range. For example, "[a-z]" matches any lowercase alphabetic character in the range a through z. |
[^ m-z ] | A negative range characters. Matches any character not in the specified range. For example, [^m-z] matches any character not in the range m through z. |
\b | Matches a word boundary, that is, the position between a word and a space. For example, er\b matches the er in never but not the er in verb. |
\B | Matches a non-word boundary. ea*r\B matches the ear in never early. |
\d | Matches a digit character. Equivalent to [0-9] . |
\D | Matches a non-digit character. Equivalent to [^0-9] . |
\f | Matches a form-feed character. |
\n | Matches a newline character. |
\r | Matches a carriage return character. |
\s | Matches any white space including space, tab, form-feed, etc. Equivalent to [ \f\n\r\t\v] . |
\S | Matches any nonwhite space character. Equivalent to [^ \f\n\r\t\v] . |
\t | Matches a tab character. |
\v | Matches a vertical tab character. |
\w | Matches any word character including underscore. Equivalent to [A-Za-z0-9_] . |
\W | Matches any non-word character. Equivalent to [^A-Za-z0-9_] . |
\ num | Matches num, where num is a positive integer, denoting a reference back to remembered matches. For example, (.)\1 matches two consecutive identical characters. |
\ n | Matches n, where n is an octal escape value. Octal escape values should be 1, 2, or 3 digits long. For example, \11 and \011 both match a tab character. \0011 is the equivalent of \001 &1. Octal escape values should not exceed 256. If they do, only the first two digits comprise the expression. Allows ASCII codes to be used in regular expressions. |
\x n | Matches n, where n is a hexadecimal escape value. Hexadecimal escape values must be exactly two digits long. For example, \x41 matches A . \x041 is equivalent to \x04 &1 . Allows ASCII codes to be used in regular expressions. |
\\$ | Escapes $ . |
\l | Changes the case of the next character to the lower case. |
\u | Changes the case of the next character to the upper case. |
\L | Changes the case of all the subsequent characters up to \E to the lower case. |
\U | Changes the case of all the subsequent characters up to \E to the upper case. |